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(No Model.)

T. A EDISON 8a E. T. GILLILAND.

TELEPHONE UIRGUIT.

No. 340,709. Patented Apr. 27, 1886.

INVENTDRS; QM a- (iJ u FFTEHS. mwumom mer. Wahinllon. 04 c.

UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF MENLO PARK, NEW JERSEY, AND EZRA T. GILLI- LAND OF BOSTON, MASSACHUSETTS.

TELEPHONE-CIRCUIT.

SPECIFICATION forming part of Letters Patent No. 340,709, dated April 2'7, 1886,

Application filed October 14, 1885. Serial No. 179,864.

To alt whom, it may concern:

Be it known that we, THOMAS A. EDISON, of Menlo Park, in the county of Middlesex and State of New Jersey, and EZRA T. GILLI- LAND, of Boston, in the county of Suffolk and State of Massachusetts, have invented a certain new and useful Improvement in Telephone Circuits, of which the following is a specification.

Heretofore in the use of telephone-receivers, difficulty has been experienced from the secondaryof the induction-coil of the transmitter of the same instrument being in circuit with the receiver. The extra currents induced in the wire of the coil have been found to reduced the volume of sound received very materially.

The object of our invention is to overcome this difiiculty, and to this end we provide means whereby the induction-coil may be cut out of circuit when the receiver is in use and restored to the circuit when the transmitter is to be used. Such means consist of a low-resistance shunt from the line around the induction-coil and a circuit-controller in said shunt, said circuit-controller being mounted upon the receiver.

In the preferred form of our invention the circuit-controller is operated by pressure upon the ear-piece of the receiver. Such earpiece is supported loosely, and is provided with a contact-piece, to which a wire of the shunt is connected; and within the case of the instrument is placed an opposing contactpiece; to which the other shunt-wire is connected. If the ear-piece is pressed against the ear of the user, these contacts are pressed together against the force of a counteracting spring with which the earpiece is provided. Circuit is thus closed from the line around the induction-coil. When the user wishes to use this transmitter, he removes the pressure from the ear-piece and the spring forces the contacts apart, so that the circuit to the line is again through the induction-coil. The receiver may be so arranged that the ear-piece pushes into the case, or so that a portion of the case pushes into theear-piece to close the shunt.

(No model.)

Instead of using the loose ear-piece to actu- 5o ate the circuit-contro1ler,we may in some cases employ a simple push-button, mounted on the receiver, so it can be readily operated when the instrument is held in the hand.

Our invention is illustrated in the accompanying drawings, in which Figurel is a diagram of a telephone and its connections embodying the preferred form of our invention.

Fig. 2 is a section of the ear-piece of the receiver thereof.

T is any suitable transmitter, and B is the battery in the primary circuit of inductioncoil I.

L is the line including the secondary of the induction-coil.

R is any suitable receiver, of which a is the inclosing-case; b, the ear-piece, and c the diaphragm. The neck of the ear-piece!) passes through an opening in the case, and is free to move back and forth therein. At its inner end within the case the ear-piece carries a metal ring, (2. Inside the case, attached'to the front wall thereof, is the metal contact 0, to which is connected awire of the shunt S S from the line around the induction-coil I. A corresponding metal piece, 6, is also attached to the case, to keep the ear-piece straight when it is pressed in. The other wire of shunt S S is connected with ring d. Outside the case, around the neck of the ear-piece, is placed a coiled spring, f, between the shoulder g and the case.

In using the receiver, if the sound is not loud enough, the user simply presses the receiver more 'closely against his ear, which brings the ring (1 against 6 e, and closes S S around I the induction -coil. When he is through listening, he removes the pressure and the spring f throws the ear-piece back to its normal position, breaking the shunt and mako ing the line read y for the use of the transmitter. Preferably the wires S S and the line-wires are all run together to the receiverin a four ply cord.

What we claim is 9 5 1. The 00mbinati0n,with a telephone transmitter and receiver and an induction-coil in the line, of a shunt around the induction-coil and a circuit-controller in said shunt carried This specification signed and witnessed this by the receiver, substantially as set forth. 2d day of January, 1885.

2. The combination, with a telephone-trans V mitter and its induction-coil, of the receiver 5 having a loose ear-piece and a shunt-circuit around the induction-coil controlled by the W'itnesses: movement of said ear-piece, substantially as JOHN C. ToMLINsoN, j set forth. FRANK E. DONOHOE. 

